I think that is just to refer to the instruction set that is being emulated (8-bit AVR - see Erin Ptacek's blog post about it on sockpuppet.org), used by the mi

I think that is just to refer to the instruction set that is being emulated (8-bit AVR - see Erin Ptacek's blog post about it on sockpuppet.org), used by the microcontroller on many Arduino boards